1. Technical Field
The present invention relates to a light emitting and receiving device.
2. Related Art
In semiconductor light emitting devices used in optical communications or the like, generally, a semi-transmissive mirror or a diffractive element is disposed outside of the devices so as to extract part of the emitted light. Then, adjustment of the intensity of the emitted light or the like is performed by detecting the extracted light by using a light receiving device.
For example, in JP-A-10-3691, an optical pickup device that branches light emitted from a laser diode through a spectral prism or the like and has a monitoring photo diode for detecting the branched light is proposed.
Meanwhile, recently, as a light emitting device used for a light source of a display device such as a projector, a display, or the like, a laser device having excellent color reproducibility with high luminance has been demanded. However, when a laser diode is used in a display device, there are cases where sufficient luminance cannot be acquired without using a plurality of laser diodes. In such a display device, in order to reduce the unevenness of luminance, the intensity of light of the light emitting device needs to be detected, and the intensity of light needs to be adjusted.
However, in the above-described method disclosed in JP-A-10-3691 or the like, a light emitting device and a light receiving device are separately arranged. Thus, additionally, an optical element such as a spectral prism or the like is necessary. Accordingly, the number of components is increased, and miniaturization of the device cannot be easily achieved. In addition, there is a problem that light receiving elements cannot be individually arranged easily although the intensity of light of each of the laser diodes needs to be detected for applying the above-described method in a display device. In addition, when a laser diode is used in a light emitting device, speckle noise, which is generated by mutual interference of scattered light on a screen surface, may cause a problem. In order to reduce speckle noise, as a light emitting device, using a general LED (Light Emitting Diode) may be considered. However, there are some cases where sufficient output power cannot be obtained from an LED.